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Monday, September 12, 2011

hurricane, part three: rivers

Reprinted with permission from the Valley News.

Royalton -- For a while, the outlook seemed dire. Few people had imagined seeing such things floating downstream: cars, propane tanks, dead cows, filmy sewage. For days after the rains ceased, pieces of homes and remnants of lives drifted past in the brown, roiling floodwaters, and even as the human impact of Tropical Storm Irene rose to the forefront, many residents worried about the health of the region's beloved rivers.

Now, almost two weeks later, a consensus is emerging: from an ecological standpoint, it's not as bad as it could've been. Vermont’s watersheds and fish populations are still reeling from what one Dartmouth researcher called a 500- to 1,000-year flood, but thanks in part to the state's reforestation and relative lack of industrial development, experts agree that recovery shouldn’t be too far in the future.

“The river will recover,” said Mary Russ, Executive Director of the nonprofit White River Partnership. “How long, I don't know, but generally … a flood is a short-term event with a short-term impact. Nature knows what it's doing.”

Not only that, but for the long-term health of rivers such as the Ottauquechee, the Connecticut, the Ompompanoosuc and the White -- as well as the many streams and tributaries that feed them -- flooding can have a positive effect.

“I know people don't like to hear this, but floods are an important ecological agent, as well as an important geomorphic agent,” said Frank Magilligan, a Dartmouth geography professor who studies flood ecology. “A lot of ecosystems have some demand for disturbance.”

Magilligan said certain niche species, such as the cobblestone tiger beetle, depend on flooding to create the pebbled island habitat they favor. Nearly every fish species, he added, needs the occasional flood to “mix things up,” creating the woody debris they love to hide under. And New England's once-extensive floodplain forests, filled with silver maples and cottonwoods, require floodwaters for their continued survival in the fight against invasive aquatic plants and land development.

“Some disturbance is good for the entire spectrum of the ecosystem,” said Magilligan, who has studied flood ecology for more than three decades.

Some disturbance, yes. But Irene's devastating floods went above and beyond, introducing a new set of variables into the natural system of flood and ebb. Magilligan estimates that, statistically, Irene was an event that occurs every millennium or half-millennium.

Nonetheless, in some places, such as at the U.S. Geological Survey gauge on the White River in West Hartford, the infamous flood of 1927 eclipsed that of Irene. Strafford resident Ken Alton, who worked with hydroelectric and flood control dams in the region for more than 40 years before retiring, said that in 1927, the flow of the White River peaked at 120,000 cubic feet per second.

One way to visualize a cubic foot of water is to think of it as a unit the size of a basketball -- then picture 120,000 basketballs rushing past at every second.

After Irene finished dumping up to a foot of rain over the spine of the Green Mountains, the White River -- which is the longest free-flowing river in Vermont, the longest undammed tributary of the Connecticut and the recipient of much of the rainwater that falls on the eastern Greens -- peaked at “only” about 80,000 cfs. The typical river flow in late summer is about 8,000 cfs, Alton said. He's seen it as low as 60 cfs.

“Never in my career did I envision this,” he said.

In other places, though -- such as the Saxtons and Black Rivers in southeastern Vermont -- Magilligan said river levels were well above those from 1927 or 1938, when another hurricane hit. “In some places, they were 100 percent greater than the largest measured discharge,” he said.

What's striking about Irene's impact is that today, 80 percent of Vermont is forested. Earlier in the 20th century, only 20 percent of the state was tree-covered; the rest had been largely cleared for horticulture and pastureland. Vegetation absorbs rainwater, leaving less of it to flow into streams and watersheds, and it also acts as flood protection for rivers, with root systems keeping soil intact and preventing erosion and sediment runoff.

Additionally, the '27 flood occurred in November, when trees weren't photosynthesizing. Bare trees take up less water than those with leaves.

That Irene surpassed previous flood records even against such mitigating factors as timing, forestation and agricultural land use is one of the reasons Magilligan thinks it's likely the biggest flood event in a century, if not longer.

***

Not only was the magnitude of Irene beyond the scope of typical river flooding, but a host of contaminants and debris were introduced into the Connecticut River and its tributaries.

Russ and his wife, director Mary Russ, were at their Royalton office on Wednesday morning preparing to collect water samples along the White River. Their organization aims to restore the health of the river corridor for both wildlife and human recreation, Mary said, so the two pay a lot of attention to water quality.

“We test for three parameters,” she added. “Bacteria, turbidity and conductivity. We anticipate that bacteria will be off the charts.”

Sure enough, when Russ sent in the results yesterday, seven of the nine sites tested on the White River failed to meet Environmental Protection Agency standards for “swimmable” water. The EPA states that 235 E.coli samples per 100 ml water sample is considered acceptable for recreational uses; the results from Sept. 7 measured as high as 1,413 E.coli samples (in Tunbridge). Details can be found at www.whiteriverpartnership.org.

High levels of coliform bacteria, from human and animal feces and soil, are not necessarily harmful to either human health or that of the river ecosystem. But the presence of fecal coliform is an indication that other pathogenic bacteria could also be present. Common sense would dictate that swimming should be avoided until the water quality improves.

The good news, though, is that because they're organic materials, bacteria break down and filter out of rivers quickly. “Usually after a flood we see a link between water quality and water clarity,” Mary Russ said. “As soon as it clears up, the water quality will improve, even this season. I don't think we have to wait until next season for the water quality to be safe for swimming.”

An official from the Vermont Department of Healthsaid that his agency neverrecommends swimming in rivers because, unlike designated public swimming sites, they are not tested by the state.

Other contaminates, such as heavy metals like mercury and lead, take longer to dissolve, but again, there's good news. Magilligan, the Dartmouth researcher, said Vermont's rural landscape means less runoff from roads and industries than there might be in more urbanized areas. Even the time of year, he said, works in favor of water quality: because it was closer to harvest season, there may have been fewer pesticides or fertilizers to wash into rivers.

Results on conductivity testing for heavy metals were not available this week. Liquefied propane, which was contained in thepropane tanks that washed into the Ottauquechee, dissipates into the air, posing little environmental hazard.

Oddly enough, the water quality indicator most troubling to the ecological health of watersheds doesn't come from sewage or floating chunks of manmade debris seeping out chemicals. It's from the sediment that entered waterways through eroded streambanks and washed-out roads. Plain old dirt. Or, in scientific terms, turbidity.

“What really surprised me was how sediment charged the water was,” Magilligan said. “New England has one of the lowest levels of sediment discharge in the country, but this was really choked with sediment.”

Turbidity can provide food and shelter for dangerous pathogens, and increased turbidity is considered to have caused “significant cases” of gastroenteritis in the U.S., according to the EPA. But perhaps the wildlife that depends on clear, cold waters suffers the most from the sediment suspended in rivers and streams.

***

For Ron Rhodes, head fly-fishing guide at Hanover Outdoors, the season is over. Fall usually presents excellent fishing opportunities, but this year “there's not a whole lot of work,” he said. “No more trips in Vermont.”

Many smaller fish were swept far downstream, while those able to resist the flood's power tried to seek calmer waters, such as those in floodplain areas. When waters receded, however, many of the trout, walleye and the few Atlantic salmon that managed to spawn this far upstream were generally left to die on dry land, experts said. Rhodes noted that he's come across a number of dead fish while cleaning up along the White River.

“There unquestionably was damage to the fish populations during this flood,” wrote David Deen, river steward for the Connecticut River Watershed Council, in a report, though the extent of the damage is difficult to document since so many dead fish would have been swept downriver.

The sediment that continues to choke rivers and streams is likely affecting fish that survived the flooding itself. Sediment particles are abrasive to fish gills, making breathing difficult. Lacerated gill tissue also provides an entry for toxic chemicals to enter the bloodstream, Deen wrote.

The problems confronting fish are further compounded by the decimation of their food supplies, in the form of washed-away aquatic invertebrates and their eggs.

The turbidity of the water may prevent invertebrates from laying eggs or hatching, and fish face the same problem.

“We're concerned how this is going to affect spawning,” said Rhodes, referring to the annual autumn reproduction of brook and brown trout. Rainbow trout, which spawn in the spring, will perhaps be less affected, but as a hardier non-native species introduced from the West, rainbows are also less of a priority for conservationists.

Even more than other coldwater species, brook trout require clean, clear water. They're are a prime indicator species for water quality. They also need gravel river bottoms to lay their eggs, so sediment build-up may hamper their efforts to procreate.

Rich Kirn, a Vermont fisheries biologist, said that full population recovery could take anywhere from one to five years, depending on location.

At the White River National Fish Hatchery in Bethel (which breeds Atlantic salmon to release into Connecticut River tributaries as part of a reintroduction effort), hatchery manager Ken Gillette said that flooding wiped out Atlantic salmon stock by 50 percent, or about 7,500 fish. Additionally, about 40,000 lake trout fingerlings destined for the lower Great Lakes were lost. The financial impact has not yet been assessed.

Kirn added that the state-run Roxbury Fish Hatchery lost more than 70,000 of its90,000 brook and rainbow trout, but that four other state fisheries were untouched. “We will have some declines, but there are certainly still quite a few fish we'll be stocking,” he said.

“One of the major points is these populations have evolved to withstand these kinds of events,” Kirn added. “This is a devastating flood and we will see an impact, but these fish are resilient and the population will rebound.”

There will be no bans on fishing, and Fish and Game's Kirn doesn't think eating caught fishposes a threat to human health. Rhodes, however, said he personally wouldn't eat fish from waterways affected by the flooding. The health department deferred the matter to Fish and Game.

While it might seem that fish -- and fishermen -- bore the brunt of Irene's ecological damage, many other species depend on a healthy fish population for their own survival. Bald eagles, mergansers, herons, raccoons, mink and otters all hunt for fish, and migrating birdsuse the waterways for water and shelter.

***

Eroding streambanks do more than deposit silt. They also factor into waterways that change their course, reverting back to the floodplains and valleys they once occupied before mills and dams diverted them and people began farming and living on land that had once been at the mercy of rivers.

While fish populations, water quality and human recreation are all expected to recover in a relatively short time -- a few years at most -- Magilligan, the Dartmouth professor, said Vermont's physical landscape will experience the most long-term effects of the flooding.

Stream channels that were considerably altered, wiping out roadways and agricultural land as well as natural habitat, could take up to ten years to return to pre-Irene dimensions and slope, he said. Trees and plants torn away from riparian buffers -- the strips of vegetation lining streambanks -- will also take some time to come back, though again, recovery may be expedited.

“Vegetation is an important vehicle by which channels recover, and on the humid East Coast … vegetation comes back pretty quickly,” Magilligan said. “That's the charm of the East Coast. Something like the scale of Irene in Utah would have an impact of 50 or 100 years.”

Mary Russ, of the White River Partnership, said that rivers changing their course and flooding their banks is inevitable, especially as climate change continues to bring an increase of severe weather events to the region. While fertile floodplains have long been a mainstay of Vermont agriculture, Russ said that farmers and landowners can take steps to mitigate against future damage.

Allowing a riparian buffer to grow, or planting one with native vegetation, is an important consideration. A buffer not only provides natural habitat for birds and fish, which enjoy shady overhangs, but also prevents erosion and helps keep the river on-course. Russ noted that several places along the White River that had utilized man-made riprap, or large stones deposited on an eroding bank, were wiped out, while several hundred yards away, areas with natural riparian buffers held up far better.

Another option, for those willing to consider it, is to step back and let the river run its course.

Several months ago, Jennifer Megyesi, owner of Fat Rooster Farm in Royalton, applied to the state's River Corridor Easement Program for her 3½ acres abutting the White River. Under the program, the Vermont Land Trust and the White River Partnership agreed to purchase development rights to Megyesi's land. Megyesi took the money -- approximately $10,000 -- and in exchange, she agreed to maintain a 50-foot buffer along the banks and prohibit future development.

The land can still be used for agriculture.

Megyesi said that this past summer, a crew of 30 volunteers planted 1,100 trees to stabilize the riverbanks, which were already eroding from a history of intensive clearing and dairy farming.

The eroding riverbanks were depositing silt into the water, which diminished habitat for fish and other wildlife.

“Ours is an organic farm, and we've always tried to curtail our farming practices with conservation in mind,” she said.

Neither Megyesi's home nor her farm were damaged by the flooding, but the land set aside as a river corridor easement was completely flooded.

She said she feels very fortunate.

“We took (that land) out of production,” she said, “so we didn't feel that loss.”

Krista Langlois can be reached at klanglois@vnews.com or 603-727-3305.

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About Me

I'm Krista. I write stories about the intersection of people, places and nature. Formally, I'm a contributor at High Country News, a non-profit environmental news magazine once called "a scrappy institution that produces some of the finest journalism in the American West." My work has also been published in Slate, Orion, Alaska magazine, New Zealand Wilderness magazine, the Denver Post, Adventure Journal, and a number of other newspapers and websites. See more at www.kristaleelanglois.com.